Hydraulic pump or motor



Aug. 29, 1950 Filed March 22, 1945 J. GREENHUT 2,520,632

HYDRAULIC PUMP 0R MOTOR 4 Sheets-Sheet 1 IN V EN TOR.

JZJTIP/l @rznw/u 7' @MMW Aug. 29, 1950 J. GREENHUT 2,520,532

HYDRAULIC PUMP OR MOTOR Filed March 22, 1945 4 Sheets-Sheet 2 INVENTOR. J'wew/ 6651mm? 29, 1950 J. GREENHUT 2,520,632

HYDRAULIC PUMP 0R MOTOR I Filed March 22, 1945 4 Sheets-Sheet s 1950 J. GREENHUT 2,520,632

- HYDRAULIC PUMP 0R MOTOR Filed March 22, 1945 4 Sheets-Sheet 4 INVENTOR. JZJtf/l infirm/4r Patented Aug. 29, 1950 HYDRAULIC PUMP OR MOTOR Joseph Greenliut, University Heights, one, as-

aignor to The Tom Electric Manufacturing Company, Cleveland, Ohio Application March 22, 1945, Serial No. 584,172 12 Claims. (Cl- 103-162) This invention relates to hydraulic pumps or motors, and particularly to devices of this type which embody a multiplicity of parallel cylinders having reciprocating pistons therein mounted in a rotating barrel.

The primary object of this invention is to provide a more durable pump or motor of the type mentioned which is evenly balanced and which eliminates transverse stresses and strains therein.

Another object is to provide a device of this type that has plungers or pump units of balanced capacity simultaneously exerting pressure and causing suction equally around an aligned pintle and drive shaft and on the same plane therewith.

A further object is to provide a rotating and reciprocating piston type pump with adjustable concentric swash plates which regulates the length of piston stroke.

Still another object of the invention is to provide a rotary fluid valve means for a pump or motor of the type stated which permits a simultaneous feeding and exhausting of balanced rotating pump units or cylinders.

A still further object is to construct a hydraulic pump or motor with a rotating barrel which has an inner series and an outer series of concentrically arranged plungers and cylinders of balanced capacity.

These and other objects, features and advantages of the invention will become apparent from a reading of the following description and claims, together with the accompanying drawings, in which like parts are referred to and indicated by like reference characters and wherein:

Figure 1 is a top or plan view of the pump, partly in section;

Figure 2 is a vertical longitudinal sectional view of the device, taken along the line and in the direction of the arrows 2-2 of the Figure 1;

Figure 3 is a vertical cross-sectional view of the device, taken along the line and in the direction of the arrows 3-4 of the Figure 2;

Figure 4 is a vertical cross-sectional view of the device, taken along the line and in the direction of the arrows 4-4 of the Figure 2;

Figure 5 is a vertical cross-sectional view of a part of the device, taken along the line and-in the direction of the arrows 5-5 of the Figure 2;

Figure 6 is a vertical cross-sectional view of a part of the device, taken along the line and in the direction of the arrows 6-6 of the Figure 2;

Figure 7 is a vertical cross-sectional view of a part of the device, taken along the line and in the direction of the arrows l'| of the Figure 2:

Figure 8 is a diagrammatic view of the conmotor or 2 centric series of plunger portions in the device. and particularly showing how forces thereof are balanced;

Figure 9 is an enlarged elevational view of a portion of the pintle member, slightly distorted, showing conduits, grooves and channels therein; and

Figure 10 is a schematic illustration of the summation of forces exerted against the barrel member at certain grooves in the pintle member.

Conducive to a clearer understanding of this device, it should be pointed out that the invention may be used either as a variable displacement type motor, as a pump, or for any other similar hydraulic power transmission. For clarity and simplicity, it will be referred to hereinafter as a pump and its elements as well as its operation will be described accordingly.

The device broadly consists of four main members; namely, the housing member, the pintle or valve member, the barrel member, and the swash plate member. Each of these members are broadly indicated by the reference characters It, 28, 40 and 10 respectively and each will be described in detail hereinafter and in the order set forth.

The housing member It consists of .a hollow case which is provided with legs or supports H for mounting the pump on any suitable base. The front end of. the case is closed with the cover or end plate l2 which is securely held in place by the bolts I20. as shown, which engage the edge of the case. This closure I! has a central opening therein and has thereat a bearing l3 for the hereinafter described shaft portion 41. This cover plate I! also has integral therewith a yoke 12. This yoke is provided with a pair of laterally extending aligned pins or bearings, indicated by the reference characters It or Ila, which support the hereinafter described swash plate member Ill. It also has a fluid seal l3a slightly forward of the bearings l 3 and concentric therewith.

The rear end it of the case has a central axial opening which is aligned with the aforesaid central opening in thefront cover l2 and which may be securely closed by the plate l5 and bolts lia. The rear end It also has a channel or passage therethrough for admitting fluid to the pump. This is indicated and referred to as the fluid entrance IG. Above it there is a similar passage referred to and indicated as the fluid egress ll.

- Both the entrance l6 and the egress I! are threaded to receive suitable ducts or conduits. The passages l6 and I! open into the axial opening or bore it, which extends longitudinally hereinafter described. barrel member 40.

through the rear portion it of the housing member. The inner end wall of the case adjacent to the end portion l4 isprovided with a support for the bearing 43 which 'in turn supports the This bearing 43 is concentric with and fits around the barrel member 40 is accurately lapped on and fitted to the pintle on which it rotates, and since it is an extremely difiicult matter, while manufacturing, to precisely align the axial opening or journal 4| with the longitudinal bore l3,

considerable wear and stress will be avoided if the pintle member 20 fits rather loosely in the bore l3. The life of the pump is prolongedconsiderably and a smoother operation of the device is obtained. The pintle member 20 is held in place and prevented from making excessive longitudinal movement or rotation by the small key or pin 21 which extends radially through the end portion l4 of the housing, as shown in the Figures 1 and 2. ,7

Four parallel ducts or channels, referred to herein as conduits 2|,22, 23 and 24, extend longitudinally through the pintle member 20. The two conduits 23 and 24 are referred to as pres sureconduits and have a joint and somewhat radially extending channel 26 which leads or opens into the egress passage II, as is shown in the Figure 7. The two conduits 2| and 22, known ,as suction conduits, similarly have a Joint radially extending channel which connects with the fluid entrance I6.

' At this point it should be noted that the Figure 9 is somewhat exaggerated and distorted to more clearly show the conduits 2|, 22, 23 and 24. Actually the said conduits are evenly spaced apart somewhat as illustrated in the Figures 5, 6 and 7.

The forward end of the first suction conduit 2| opens into a first arcuate or peripheral groove 3| in the pintle member 23 by way of the radial channel 35. The first pressure conduit v 23 similarly opens at its forward end into a second arcuate groove 33 by way of the radial channel 31. The second suction conduit 22 opens at its forward end into a first pair of arcuate or peripheral grooves 32 and 32a by way of the radial channels 36 and 36a, as is shown in the Figures 5 and 9. Similarly, the second pressure conduit 33a. Each of the arcuate peripheral grooves 3| and 33, and each of the grooves 32, 32a, 34 and 341;, are of the same length and cover an arc a little less than 180 degrees. The grooves 3| and 33 are diametrically aligned and are opposite each other as shown, and similarly the grooves 32 and 34 are aligned opposite each other, asalso are the grooves32a and 34a. The channels 3| /33 are between the channels 32/34 and 3211/3411.

At thispoint it should be noted that by providing two sets of grooves 3|, 32 and 32a and 33, 34 and 34a and ducts thereto instead of only one set, and by having the large grooves 3| and 33 between the small grooves 32 and 32a and -3 and 34:: respectively, a better'balance of forces the pump as hereinafter set forth in detail, that if only grooves 32 and 34 and related ducts are used, with the large grooves 3| and 33, and if grooves 32a and 34a. were eliminated entirely the pressure or lack of pressure of the fluid in the radial grooves and ducts 35 and 31 would tend to force the barrel member 40 out of line or askew, and in time wear of the parts would be noticeable.

The area of the large groove 3| is equal to the sums of the areas of the two small grooves 32 and 32a. Similarly the area of the large groove 33 is equal to the'areas of the two small grooves 34 and 34a. In the preferred form of the device as illustrated, it is desirable to have the areas of the small grooves32 and 34 equal to the areas of the small grooves 32a and 34a respectively. However, it is notessential that the areas of the small grooves 32 and 34 be the same. The areas thereof may be varied depending upon their distance from the corresponding or interconnected large groove. The fact to be noted is that the algebraic sum of the moments or torques about the pivotal axis of the pintle member 23 proximate to the large grooves 3| and 33, should be zero. As defined in the claims the sum of the moments produced by the fluid pressure in each set of grooves acting against the barrel member about a planev perpendicular to the axis of the pintle member is zero.

In other words, the hydraulic pressure in the large groove 3|, is equal at all times to the by draulic pressure in the two opposed grooves 32 and 32a. Similarly at all times the hydraulic pressure in the large groove 33 is equal to the pressure in the two opposed grooves 34 and 34a. However it should be clearly understood that the hydraulic pressure in the two sets consisting of grooves 3|, 32 and 32a in grooves 33, 34 and 34a need not be equal. For example, the device when used as a pump may have a positive pressure of one hundred pounds per square inch applied to the set of grooves 3|, 32 and 32a and at the same time the set of grooves 33. 34 and 34a may have a negative pressure or suction of tenpounds per square inch therein.

In the preferred construction the set of grooves which are in hydraulic communication with the discharge of the pump are of suchsize and location that no unbalanced forces or moments are produced by the forces exerted on the barrel by the hydraulic pressure in these grooves. This is likewise true of the set of grooves which are in hydraulic communication with the suction of the pump.

Assuming that the groove 33 is collecting the fluid being pumped out of certain cylinder bores, this fluid then, through a radial channel 31 and the first suction conduit 23 is conducted to the discharge port I1. Grooves 34 and 3441 are also connected to the port II. The fluid passes from grooves 34 and 34a'through the radial channels 33 and 38a into the second suction conduit 24 which also opens in to the discharge port Il. Thus the hydraulic pressure is substantially the same in the grooves 33, 34 and 34a.

In the preferred form of myinvention, thegrooves are symmetrical about the horizontal axis, and also the area of the groove 33 exposed to the'bore ofthe barrel,,is substantially'equal to the sum of the areas of grooves 34 and 34a. F33 in the Figure 10 represents the resultant of the forces acting against the bore of the barrel sndduetothehydraulicpressureinthegroove' above, it will be seen that F33 is substantially equal to 1" plus l'fla. Thus there is no unbalanced force acting on the barrel due to the hydraulic pressure in this set of grooves.

Now I also contemplate, in'the preferred form of my invention, making the area of grooves It and Na of such magnitude and so locating these grooves so that the moment of F about any plane il-III perpendicular to the axis of the pintle, plus the moment of 1" about the same plane is equal to the moment of 1''" about this same plane. Or in other words:

Fromthisitwillbeseenthatthereisalsonounbalanced moment exerted on the barrel by the hydraulic pressure in this set of grooves.

New in a similar manner the other set of grooves ll, 32 andfla are also subjected to a 6 the barrel member to is mounted on and rotates on the bearings It and also rotates around the forward or front portion of the pintle member 2|,

the portion having the aforementioned peripheral grooves 3|. 32, 32a, 83. It and a therein.

The forward portion of the barrel member ll has a protruding shaft mounted therein which is any suitable driving wheel or pulley may be balanced hydraulic pressure because of their respective areas, design and location. Specifically assuming that the groove 3! is collecting fluid entering the certain cylinder bores, the fluid passes from the port It through the first pressure conduit 2| through the radial channel into the groove 3!. On the other side of the pintle the fluid passes from the entrance port It into the second pressure-conduit 22 into the radial channel 38 and "a into the grooves 32 and 32a.

Specifically, the conduits 23 and 24 which contain fluid under pressure are on one side of the pintle, while the conduits 2| and 22 which contain fluid on suction are on the other side of the pintle. The forward set of grooves 32a/34a. are blind and are closed by the rotating journaled portion ll. Nevertheless, the pressure exerted therein by the fluid which also came from the pressure conduits 2| and 22 by way of the radial channels 36:: and 38a is equal to the pressure in the corresponding grooves 32/. The barrel member is thus caused to rotate evenly on the pintle member 20 and its dynamic balance is better preserved at high speeds.

The portion of the pintle 20 in the housing end It also has four spaced parallel peripheral grooves which receive the fluid seals or rings 28, 20a. 28b and 28c. These grooves extend completely around the pintle. The first ring 28 engages the pintle 20 slightly forward of the said radial channel 28. The second ring 28a is mounted in the second groove a slight distance to the rear of the radial channel 26. .The third seal or ring 28b engages the pintle a short distance in front of the radial channel 25, and similarly the fourth ring or seal 28c fits into the last groove a short distance behind the radial channel 25. These rings 28, 28a, 28b and 28c prevent the fluid from passing at these points and flowing into the here It and ultimately into the journaled portion 4|, but they still are resilient enough. to permit the pintle 20 to move laterally slightly as aforesaid within the rear portion ll of the housing to take up undesired wear or misalignment.

The barrel member 40 has an outside diameter slightlyless than the inside diameter of the housing it. It has an axial opening therethrough which is refei'red to and indicated as the journaled portion ll. This is aligned as closely as possible with the axial opening or bore is in the rear end ll of the housing. The rear portion of mounted. This constricted portion 41 extends through the front wall or cover i2 and rides on the bearing l3 and in the fluid seal a. Between the constricted portion 41 and the engaging portion 48 there is a tapered portion 48 which passes between the rearwardly extending arms of the heretofore mentioned yoke 12 and on which the hereinafter described swash plates III are mounted.

The barrel member 40 is provided. with two series of plungers. Each series of plungers consists of several cylinders and reciprocating pistons. v,Ihe drawings show each series containing eight plungers but the invention is not restricted to the number shown. Any-odd or even number of plungers may be used in either series provided a proper balance can be obtained between the two sets or series of plungers.

The inner series of plungers 5| as shown in the drawings are shorter and larger in diameter than the plungers of the outer series 6|. The relative sizes, however, need not be the same or as illustrated. It is important only that all of the plungers have a diameter in a fixed relation to their distances from the axial center of the barrel member. The areas of the pistons are ad- :lusted in diameter in relation to their radii so that the summation of the moments produced by the forces acting on all the pistons about any plane through the horizontal axis of the device is equal to zero. One series of plungers or pistons being of such number, diameter and position that the summation of the moments produced by their reaction forces on the rotatable barrel about any plane through the axis of rotation thereof is substantially equal to the summation of moments produced by the reaction forces of the other series of plungers or pistons about the same plane.

This is schematically illustrated in the Figure 8.'wherein the summations of the forces of the pistons under pressure at any instant are taken around the plane A-B. Thus the forces of the outer set of pistons 6| under pressure and the forces of the inner set of pistons 5| under pressure times their respective moment arms to plane A-B, when algebraically totaled, are equal to zero. Specifically,

. 7 r In the drawings. the half of the plungers of 3 the inner series on the pressure side of the pump are indicated bythe reference character BI and the other half on the suction side are indicated b the reference the half of the outer series on the pressure side character 5m; and similarly of the pump are indicated by the reference character 5 l while the other half on the suction side are indicated by the character Bio. The plungers 5| of. the pressure side of the inner series are 1 directly opposite the plungers 6| of the pressure 1 side of the outer series, and similarly the plung- 1 ers Sla areopposite and balance the plungers Bia.

While the drawings, for the sake of clarity and simplicity, show specific oppositely disposed plungers in balance, they need not be so arranged.

lowing described swash plates II and H.

The swash plate member, broadly indicated by the reference character 10,- consists of two rings .II and 14 which are pivotally and laterally mounted on the arms of the horizontal yoke 12. The smaller ring II has two diametrically aligned holes therein which permit it to be pivoted and inclined with respect to the front end of the barrel member 40 on the pin portions i8 of the yoke.

1 The diameter of the small ring II is substantially If desired, the inner series may consist of an even number of plungers while the outer series i ,may have an odd number or vice versa. The

number of plungers in each respective series may be different. However, it is apparent that the smoothest and best operation would be obtainable by having the device in equilibrium as much as possible. This condition could most easily be obtained by having the design thereof in balance as much as possible.

Each plunger or piston works in a cylindrically shaped longitudinal hole or bore drilled in the housing member 40 parallel with the axis .thereof. These cylinder bores may be spaced and aligned the same as the diameter of the inner series ,of plungers tl/ 51a of the barrel member 60. The larger ring it also has diametrically aligned holes therethrough which'permit itto be tilted on the bearings or outer pin portions i8a of the yoke 12. The larger ring it fits around the smaller ring ii, is concentric therewith, and has a diameter substantially the same as the diameter of somewhat as indicated in the Figure 4 of the drawings. Each cylinder bore of the inner series has a movable piston 55 which piston has a substantial head portion 55 and a hollow portion to the rear-thereof in which there is mounted the spring 56. The springs 56 tend to drive the pis tons 5d outward and cause the piston heads 65 thereof to ride smoothly on the hereinafter described inclined swash plate rings H. Each inner cylinder bore 5! connects with the axial vopening M, which in turn opens into either of the peripheral grooves 3! or 33 on the pintle member 20, depending upon the position of the barrel member to thereon. The radial ducts or ports connecting the half of the cylinder bores 5! .on the pressure side of the-pump and which opens into the groove 33' are indicated by the reference character 52. Similarly the radial ducts or ports which connect half of the inner series of cylinder bores em on the suction'side of the pump and which open into the peripheral groove 31 are indicated by the reference character 53. In a similar manner, half of the outer series of cylinder bores 6| on the pressure side of the pump have radial ducts or ports 82 which open into the peripheral groove 36 in the pintle member, and the other half of the cylinder bores tie on the suction side of the pump each have a radial duct or port 63 which opens into the peripheral groove 32. Each cylinder bore 5! or Eia I of the inner series successively connects with the peripheral grooves '31 and 33 as the barrel member rotates around the pintle and thereby either causes a suction or exerts a pressure on the fluid flowing through the device, depending the special barrel member 40 around the special intle member 20 forms a novel valve means ,the outer series of plungers Bi/Bla of the barrel member.

have rounded edges '13 and 16 as shown. The

The swash plates or rings ii and it faces thereof on which the plungers ride are provided with suitable rollers in order to minimize the friction thereagainst of thepiston heads 55 and 85. r

- Each of the rings or swash plates ii and it are inclined in opposite directions as shown, and in order to provide a convenient means for adjusting the angle at which the respective plates ii and it are tilted, a simple but durable adjusting lever 8i and means 82 are provided. This makes it possible to conveniently adjust the device to regulate its capacity or force from outside of the housing and while it is inpperation. The Figure 2 of the drawings shows the plates H and l iinclined in opposite directions and at about the same relative angles. However, the two plates need not be so inclined or adjusted. They may both be inclined in the same direction or they might be inclined at angles of different degrees. However, as before stated, the smoothest and best operation and results are obtained when the device is balanced and the plates positioned somewhat as shown.

The control mechanism consists of a short shaft 82 rotatably mounted on and made to extend through the side wall of the housing member 80. The outer end of the shaft 82 is firmly connected to the lever 8| as shown. The inner end of the shaft .82 has mounted thereon two reciprocating arms 83 and 85. The arm 83 is connected to the smaller ring or inner swash plate H by the link, 84, and similarly the arm 85 is connected to the larger ring or outer swash plate M by means of the link 86. The arms 83 and 85 are spaced and mounted on the shaft 82 so that the movement of the lever 8| will cause the rings H and 14 to move inwardly or outconstantly retain the angles at which they areset., By referring to the Figure 2 of the drawing,

' it will be observed that by inclining the swash plates more or less, the capacities of the plungers will be increased or decreased accordingly, and by this means a very fine adjustment may be obtained for the pump regardless of mechanical imperfections or unavoidable unbalance of certain parts therein.

9 many advantages that this pump over prior art devices is the fact used at relatively high pressures practically all transverse or cross tension is substantially-eliminated or at least reduced to a minimum. It is therefore less noisy than theprior art pumps and since it may be well balanced, it is relatively free from incidental vibration and undue wear. The flow of fluid is practically constant and is noticeably free from pulsations which characterize the operation of many prior art pumps of this general type. A pump constructed in accordance with this in ventlon, being practically free of transverse or cross thrusts, eliminates the necessity of repairing the pump at frequent intervals or of replacing the bearings, valves and drive shafts therein.

Furthermore, since the pintle member is free to adjust itself to the barrel member 40 as aforestated, due to the pintle member being free to adjust itself within the housing member iii, a longer lasting unit is obtainable than would be the case if the pintle member were rigidly mounted in the housing. Vibration and shock due to misalignment are thus automatically absorbed and remedied.

It-will also be noted that this particular design of pump has relatively few moving parts under stress or strain and since its members and parts are easier to align, its ultimate cost of manufacture and assembly is therefore reduced considerably.

It will now be clear-that there is provided by this invention a device which accomplishes the objects heretofore set forth. While the invention has been disclosed in its preferred form, it is to be understood that the specific embodiment thereof as illustrated and described is not to be construed in a limiting sense as there may be other forms or modifications of the invention which could also be considered to come within thescope of the appended claims.

I claim:

l. A device of the class described, comprising in combination, a housing member, a pintle member mounted in the housing member, a rotatable barrel member having cylinder bores therein Journaled on the pintle member, an inner series of plunger portions and an outer series of plunger portions in the said bores, the said inner and outer series of plunger portions being concentrically arranged, one series of plunger portions being of such number, diameter and position that the summation of moments produced by their reaction forces on the aforesaid rotatable barrel member about any plane through the axis of rotation thereof is substantially equal to the summation of moments produced by the reaction forces of the other series of plunger portions about the same plane, concentric swash plates mounted in the housing member and engageable with the plunger portions, and means in the said members for intermittently feeding and exhausting a fluid to and from each of the said plunger portions.

. 2. A device of the class described, comprising in combination, a housing member, a pintle member mounted in the housing member, a rotatable barrel member iournaled on the pintle member,

. the said barrel member having a multiplicity of longitudinal cylinder bores therein arranged to form an inner series and an outer series of bores concentric with the axis thereof, each cylinder bore of each of the said series having a piston therein, one series of pistons being of such numl0 ber, diameter and position that the summation of moments produced by their reaction forces on the aforesaid rotatable barrel member about any plane through the axis of rotation thereof is substantially equal to the summation of .moments produced by the reaction forces of the other series of pistons about the same plane, a-

pair of swash plates mounted in the housing .member including a small plate inclined in one direction and being engageable with the pistons of the inner series of cylinders and a large plate inclined in the opposite direction and being engageabie with the pistons of the outer series of cylinders, and means in the said members for intermittently feeding and exhausting a fluid to and from each of the said cylinders.

. 3. A device of the class described, comprising in combination, a housing. a pintle member mounted in the housing and having a pair of pressure conduits and a pair of suction conduits therein, a'rotatable barrel member journaled on the pintle member, the said barrel member having a multiplicity of longitudinal plunger portions therein arranged to form an inner series and an outer series concentric with the axis thereof, one half of the inner series and one half of the outer series of plunger portions being connectable with the pair of pressure conduits during the time when the other half of the inner series and the other half .of the outer series of plunger portions are connectable with the'pair of suction conduits, one series of plunger portions being of such-number, dlameterand position that the summation of moments produced gageable with each concentric series of plunger portions.

4. A device of the class described, comprising in combination, a housing having a fluiden-.

trance and a fluid egress therein, a pintle mounted in the housing and having two pressure conduits connected to thesaid egress and two suction conduits connected to the said entrance, a barrel member rotatably mounted in the housing and journaled on the pintle, the said barrel member having a multiplicity of longitudinal cylinder bores therein arranged to form an inner series and an outer series concentric with the axis thereof, one half of the inner series of cylinder bores being in fluid communication with one of the said pressure conduits, one half of the outer series of. cylinder bores being in fluid communication with the other of the pressure conduits, the other half of the innerseries of cylinder bores being in fluid communication with one of the said suction conduits and the other half of the outer series of cylinder bores being in fluid communication with the other of the suction conduits, each of the said cylinder bores having a piston therein, and concentric swash plates mounted in the housing member and engageable with each concentric series of cylinder bore pistons.

5. A device of the type defined inclaim 4 and further characterized by one series of pistons being of such number, diameter and position that the summation of moments produced by their reaction forces on the aforesaid rotatable barrel member about any plane through the axis of maccuses tation thereof is substantially equal to the sum- I mation of moments produced by the reaction forces of the other seriesof pistons about the 8. A device of the class described, comprising in combination, a housing having a fluid entrance and a fluid egress therein, a pintle mounted in the housing and having two pressure conduits connected to the said egress and two suction conduits connected to the said entrance, a barrel member rotatably mounted in the housing and iournaled on the pintle, the said barrel member having a multiplicity of longitudinal cylinder bores therein arranged to form an inner series and an outer series concentric with the axis thereof, one half of the inner series of cylinder bores having ports connectable with one of the said pressure conduits, during the time when one half of the outer series of ports are connectable with the other pressure conduit, the other half of the inner series having ports connectable with one of the said suction conduits during the time when the other half of the outer series of ports are connectable with the other suction conduit, the said inner and outer series of cylinder bores being concentrically arranged and in a manner such that an inner cylinder bore and a port thereof are on the same plane as the axis of the barrel and an outer cylinder bore and a port thereof, andoppositely inclined concentric swash plates mounted in the housing and engageable with the barrel member.

T 7. A device of the'class described, comprising in combination, a housing having a fluid entrance and a fluid egress therein, a pintle mounted in the housing and having two pressure conduits connected to the said egress and two suction conduits connected to the said entrance, a barrel member including a shaft rotatably mounted in the housing and journaled on the pintle, the said barrel member having a multiplicity of iongitudinal cylinder bores therein arranged to form an inner series and an outer series concentric with the axis thereof, one half oi the inner series of cylinder bores having ports connectable with one of the said pressure conduits during the time when one half of the outer series of ports are connectable with the other pressure conduit, the other half of the inner series having ports connectable with one of the said suction conduits during the time when the other half of the outer series of ports are connectable with the other suction conduit, the said inner and outer series of cylindeibores being concentrically arranged and in a manner whereby an inner cylinder bore and a port thereof are on the same plane as the axis of the barrel and an outer cylinder bore and a port thereof, the said inner and outer series of cylinder bores having pistons therein, one series of pistons being of such number, diameter and position that the summation of moments produced by their reaction forces on the aforesaid rotatable barrel member about any plane through the axis of rotation thereof is substantially equal to the summation of moments produced by the reaction forces of the other series or pistons about the same plane, and two oppositely inclined concentric swash plates adjustably mounted in the housing member around the drive shaft, one of the said plates being engageable with the pistons of the inner series of cylinder bores and the other of the plates being engageable with the pistons of the outer series of cylinder bores causing the pistons in the'same plane to reciprocate harmoniously.

8. A device of the class described, comprising in combination, a housing member having a fluid entrance and a fluid egress therein, a pintle mounted in the housing member and having two pressure conduits connected to the said egress and two suction conduits connected to the said entrance, a barrel member rotatably mounted in the housing member and journaled on the pintle,

the said barrel memberhaving a multiplicity of longitudinal cylinder bores therein arranged to iorman inner series and an outer series concentric with the axis thereof, one half of the inner series of cylinder bores having ports connectable with one of the said pressure conduits during the time when one half of the outer series of ports are connectable with the other pressure conduit, the other half of the'inner series having ports connectable with one of the said suction conduits during the time when the other half of the outer series of ports are connectable with the other suction conduit, each of the said cylinder bores having a piston therein, the said inner I and outer series of cylinder bores being concentrically arranged and in a manner cylinder bores, and a valve in the said members synchronized with the reciprocation of the said pistons.

9. A pump of the swash plate type comprising a casing, a cylindrical barrel rotatable within said casing and having two concentric rows of cylinders therein; a port communicating with each cylinder, a spring retracted plunger in each of said cylinders, a fluid inlet including a passageway for communicating with a series of ports of one concentric-row of cylinders and simultaneously with a series of ports of diametrically opposite cylinders of the second concentric row, a fluid outlet including a passageway for communicating with a second series of ports of said one row of cylinders and simultaneously with a series of ports of diametrically opposite cylinders of the second concentric row, means for rotating the cylindrical barrel about its axis, whereby the ports of said cylinders are brought into successive communication with said passageways, and a pair of swash plates positioned in engagement with the ends of the plungers in each of said rows respectively, said swash plates being inclined in opposite directions with respect tothe axis of the cylindrical barrel, whereby the pistons of the cylinders in communication with the inlet passageway draw in fluid while the pistons in communication with the outlet passageway eject fluid and the forces are opposite in respect to opposite cylinders in one row and in respect to adjacent cylinders in the other row so that the sum of the moments on the swash plate structric row of cylinders and simultaneously with a series of ports of diametrically opposite cylinders of the second concentric row, a fluid outlet including a plurality of arcuate passageways for communicating respectively with a 'second series 13 of ports of said one row of cylinders and simultaneously with a series of ports of diametrically opposite cylinders of the second concentric row, means for rotating the cylindrical barrel about its axis, whereby the ports of said cylinders are brought into successive communication with said passageways, and a pair of swash plates positioned in engagement with the ends of the plungers in each of said rows respectively, said swash plates being inclined in vopposite directions with respect to the axis of the cylindrical barrel, whereby the pistons of the cylinders in communication with the inlet passageways draw in fluid while the pistons in communication with the outlet passageways eject fluid and the forces are opposite in respect to opposite cylinders in one row and in respect to adjacent cylinders in the other row so that the sum of the moments on the swash plate structure is substantially zero.

11. A pump of the swash plate type comprising a casing, a cylindrical barrel rotatable within said casing and having two concentric rows of cylinders therein, a port communicating with each cylinder, a spring retracted plunger in each of said cylinders, a fluid inlet including a passageway for communicating with a series of ports of one concentric row of cylinders and simultaneously with a series of ports of oppositely disposed'cylinders of the second concentric row, a fluid outlet including a passageway for communicating with a second series of ports of said one row of cylinders and simultaneously with a series of ports of oppositely disposed cylinders of the second concentric row, means for rotating the cylindrical barrel about its axis, whereby the ports of said cylinders successively are brought into communication with said passageways in series, a pair of swash plates positioned in engagement with the ends of the plungers in each of said rows respectively, said swash plates being inclined in opposite directions about a common axis transverse to the axis of the cylindrical barrel, whereby the pistons of the cylinders in communication with the inlet passageway draw in fluid while the pistons in communication with the outlet passageway eject fluid, and means interconnected to said swash plates and operable simultaneously to move said plates in opposite directions about their common axis to vary the stroke of said pistons.

14 12. A pump of the swash plate type comprising a casing, a cylindrical barrel rotatable within said casing and having two concentric rows of cylinders of equal number therein, the cylinders of each row being substantially in alignment radially and the cylinders of thecuter row having smaller diameters than those of the inner row, a port communicating with each cylinder, a spring retracted plunger in each of said cylinders, a fluid inlet including a passageway for communicating with a series of ports of one concentric row of cylinders and simultaneously with a series of ports of oppositely disposed cylinders of the second concentric row, a fluid outlet including a passageway for communicating with a second series of ports of said one row of cylinders and simultaneously with a series of ports of oppositely disposed cylinders of the second concentric row, means for rotating the cylindrical barrel about its axis, whereby the ports of said REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,297,734 Rayburn Mar. 18, 1919 1,714,148 Weldy May 21, 1929 1,822,064 Sorensen Sept. 8, 1931 2,129,828 Dunn Sept. 13, 1938 2,205,913 Stacy June 25, 1940 2,237,430 Higgins Apr. 8, 1941 2,328,717 Glasner Sept. '7, 1943 2,426,588 Benedek Sept. 2, 1947 2,427,224 Morton .a Sept. 9, 1947 2,445,281 Rystrom July 13, 1948 

